What is in a tool concept? Dissociating manipulation knowledge from function knowledge.

Research on patients with apraxia, a deficit in skilled action, has shown that the ability to use objects may be differentially impaired relative to knowledge about object function. Here we show, using a modified neuropsychological test, that similar dissociations can be observed in response times in healthy adults. Participants were asked to decide which two of three presented objects shared the same manipulation or the same function; triads were presented in picture and word format, and responses were made manually (button press) or with a basic-level naming response (verbally). For manual responses (Experiment 1), participants were slower to make manipulation judgments for word stimuli than for picture stimuli, while there was no difference between word and picture stimuli for function judgments. For verbal-naming responses (Experiment 2), participants were again slower for manipulation judgments over word stimuli, as compared with picture stimuli; however, and in contrast to Experiment 1, function judgments over word stimuli were faster than function judgments over picture stimuli. These data support the hypotheses that knowledge of object function and knowledge of object manipulation correspond to dissociable types of object knowledge and that simulation over motor information is not necessary in order to retrieve knowledge of object function.